Structural evidence of methanol inhibition of Candida antarctica Lipase B

Candida antarctica lipase B (CALB) is one of the most widely studied enzymes, due to its high selectivity and catalytic activity in organic and polymer synthesis. Because of the great interest in knowing the behaviour of CALB in presence of specific organic solvents, the molecular mechanism of the deactivation of the enzyme by methanol was already investigated by several researchers. In this contest, for having an understanding of the defective activity of the lipase, we addressed the inhibition pathways of CALB by methanol. The structural modifications of CALB in a methanol-water mixture were evaluated in the present work considering that the catalytic activity decreases in such mixture. The present work reports the crystal structure of the lipase in presence of methanol refined with specific crystallographic software tools, namely WinCoot, REFMAC5 and Phenix able to refine the model every time a correction is made on the enzymatic structure. WinCoot is the program used for any kind of correction at the atomic level to the crystal structure because capable to provide specific tools for intervening on the enzyme. Then, the obtained model was refined through with REFMAC5 or Phenix, both used for validating these the modifications. Having a molecular description of the interaction between solvent and enzyme is prerequisite to a qualitative understanding of enzymatic activity in organic solvents.